I'm really happy with my new Dell precision M6400.
The only thing most people complain about is the size of the power brick, and I can't agree more. It's a huge 200 Watt thing and it's really as large and heavy as a stone brick.
Luckily I still have a spare power brick of my old Dell precision M65: a 90 Watt PA-10 family power brick. It has exactly the same voltage (19.5 Volt) so I decided to try it.
I've been using it now for a few days when at customer sites and it works fine.
(Try at your own risk!)